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Decreasing the Chance of Birth Defects
by Rebecca D. Williams
When Tammy Troutman of Knoxville, Tenn., was planning her first pregnancy, she had a good reason to be concerned about birth defects.

Born with a mild form of spina bifida, Troutman worried her child would also have the condition. So she did what health-care experts say is the best first step toward preventing birth defects: She visited her physician for an exam well before she and her husband tried to conceive.

"Before I decided to have children, I went to the doctor to make sure everything would be OK," Troutman remembers.

He advised her to take a daily multivitamin supplement containing folic acid, a B vitamin that would decrease her chances of having a baby with spina bifida. Troutman took the vitamins for five months before conceiving her son, Evan, who was born in August 1993 with a normal, healthy spine.

"Even if he had been born with spina bifida," Troutman says, "I felt secure knowing that I had done everything I could to prevent it."

Of the 4 million infants born annually in the United States, about 3 to 5 percent are born with birth defects, according to the March of Dimes. Birth defects account for 20 percent of all infant deaths in the United States, more than from any other single cause.

"For the majority of birth defects, the cause is unknown," says Franz Rosa, M.D., a pediatrician, formerly with the Food and Drug Administration, who monitored reports of prescription drugs causing birth defects. Rosa cites a list of drugs that are known to be birth-defect causing, but he says they only account for a small percentage of all malformations.

"There's a lot we just don't know," Rosa says. "Most birth defects are not preventable and mothers should not feel guilty about causing defects that they really didn't. Worrying too much is not good for pregnancies."

What experts do know is that most birth defects occur in the first three months of pregnancy, when the organs are forming. It is in these crucial first few weeks--often before a woman even knows she's pregnant--that an embryo is most susceptible to teratogens, substances that can cause defects. However, some birth defects do occur later in pregnancy as well.

"The key is what your life is like at the time you become pregnant," says Deborah Smith, M.D., an obstetrician and gynecologist in FDA's Office of Women's Health. "Are you getting enough folic acid, are you immune to rubella, are you avoiding alcohol and smoking? These are some of the things we know are important."

Despite the benefits of seeing a doctor before conceiving, only 26 percent of women planning a pregnancy do so, according to the March of Dimes. Furthermore, health experts estimate more than 50 percent of pregnancies are unplanned. That's why a healthy lifestyle for all women who could become pregnant--even if they don't intend to--is the best way to minimize the risk of birth defects.

Healthy Diet

The maxim "You are what you eat" is sterling advice during the first three months of pregnancy.

Studies of women who had endured starvation during World War II illustrate the importance of diet early in pregnancy. Contrary to what researchers expected, it was not the babies born during food deprivation that had the most malformations, but those conceived during food deprivation.

One nutrient known to prevent birth defects is folic acid, the B vitamin Tammy Troutman took before her pregnancy. Folic acid is the chemical form of folate, which is found in green leafy vegetables, citrus fruits, and legumes. Folate aids in cell division, and taking extra folic acid reduces a woman's chance of having a child with spina bifida and other abnormalities of the spine and brain.

Spina bifida occurs when the vertebrae do not close completely. It is one of several conditions known as neural tube defects, because the neural tube is the portion of the embryo that develops into the brain and spinal column. In very mild cases, spina bifida causes few or minor problems, but in more severe cases, the spinal cord protrudes through the vertebrae into a sac outside the child's body. This impairs the child's mobility and other neurological functions and requires surgery to repair the opening.

To help prevent neural tube defects, the U.S. Public Health Service has recommended that all women of childbearing age who are capable of becoming pregnant consume 0.4 milligrams (mg) of folic acid per day. (For pregnant or lactating women, the daily value increases to 0.8 mg per day.) It is especially important that women take in sufficient folate before they become pregnant.

FDA recently published regulations requiring manufacturers to add folic acid to enriched grain products such as flour, noodles, bread, rolls, buns, farina, cornmeal, grits, and rice by January 1998. (See "How Folate Can Help Prevent Birth Defects".

Although the main challenge in pregnancy is getting enough nutrients, too much of a good thing is not good for a developing baby, either. Vitamins A and D are the most notable examples. Both can be toxic at levels higher than the recommended daily allowance. Such levels are rarely reached through food intake; however, women taking dietary supplements need to be aware of this risk and the amount of these vitamins they are taking. Women who take vitamin and mineral supplements should discuss with a health-care professional what vitamins are safe to continue taking during pregnancy.

Only a few foods are completely off-limits during pregnancy. These include raw or undercooked meat, such as "pink-in-the-middle" burgers, and raw or undercooked seafood. Bacteria from these can cause severe food poisoning, which is dangerous to a fetus and very unpleasant for the mother.

Soft drinks, coffee, tea, and other caffeinated drinks can be used in moderation. Although large doses of caffeine have caused skeletal defects in rats, one or two cups of coffee daily are not considered dangerous for developing fetuses.

Alcohol should be avoided at all times during pregnancy because it leads to low birth weight and can cause deformities as well.

According to the March of Dimes, alcohol is the most common known cause of fetal damage in the country and the leading cause of preventable mental retardation. Pregnant women who drink alcohol, especially in large amounts, put their babies at risk for fetal alcohol syndrome, which causes growth retardation, facial deformities such as a small head, thin upper lip, and small jaw bone, an underdeveloped thymus gland, and mental deficiencies or developmental delays.

If a woman has had a glass or two of wine before finding out she was pregnant, she probably has not harmed her child. But since no one knows the exact amount of alcohol that is dangerous, it's best to avoid alcohol when pregnancy is possible.

Healthy Mothers, Healthy Babies

A pregnant woman who has a serious medical condition may face a greater than normal risk that her child will have a birth defect.

Diabetes, for example, can complicate a pregnancy in many ways. Women who must take insulin daily to control their blood sugar are three or four times more likely to have a baby with major birth defects than are other mothers. That's not to say they should abandon insulin, however. Without it, many diabetic women and their babies wouldn't survive pregnancy at all.

Birth defects among diabetics can be greatly reduced if women get their blood sugar levels under control before becoming pregnant and strictly manage their diets throughout pregnancy. Gestational diabetes, which develops during pregnancy, can also be harmful to mother and child, but it can be controlled through diet or medication.

Epilepsy also increases a woman's chance of having a baby with a birth defect. It's not clear whether the disease itself or the drugs used to control it cause malformations, but in either case, the woman's neurologist and obstetrician should work together to find the safest course of treatment for the epilepsy and pregnancy.

Rubella, toxoplasmosis, cytomegalovirus, and syphilis can cause birth defects in the infants of women who have these infectious diseases. Rubella infection during early pregnancy can cause abnormalities of the heart, eyes and ears. Any woman planning a pregnancy should be tested for rubella immunity and vaccinated if necessary. She must wait three months after vaccination before becoming pregnant, however, because the vaccine itself can endanger a developing fetus.

Toxoplasmosis is transmitted only through raw meat and cat feces, both of which pregnant women should try to avoid. The disease causes malformations of the brain, liver and spleen if a fetus becomes infected in the first trimester.

If a woman has syphilis, she should be treated with antibiotics before pregnancy. If not treated by at least the fourth month, syphilis can cause bone and tooth deformities in the baby, as well as nervous system and brain damage.

Cytomegalovirus (CMV) is a herpes virus that causes no real problem--and sometimes not even symptoms--for adults and children. In pregnancy, however, it can damage the fetus' brain, eyes or ears. Because most people contract the infection, whose symptoms are very much like a cold, when they are children, most adults are immune to it. Pregnant women who do not know if they've had CMV and who work with large groups of young children should discuss the situation with their health-care providers.

Sometimes it is not a disease that causes birth defects, but the medication used to treat it. Unfortunately, no one knows for certain how most drugs will affect a developing fetus. Historically, most women of childbearing age have been excluded from clinical trials of new drugs, and, although that is changing, drug manufacturers are understandably reluctant to involve pregnant women in clinical trials for new drugs. Therefore, the effects of many drugs are not known until they are in wider use after market approval.

To be on the safe side, a pregnant woman shouldn't take any drug unless it is absolutely necessary and not until she's checked with her health-care provider. However, even physicians have little information when prescribing medication for pregnant women. What is known about most drugs in pregnancy is based either on animal studies or on reports of problems after the drug is on the market. To give guidance about pregnancy safety, FDA requires that manufacturers include in the professional labeling for each drug which one of several categories, reflecting information from studies available at the time the label was developed.

Two examples: Taxol (paclitaxel), used to treat ovarian and breast cancer, may in some instances be appropriate in pregnancy even though it causes birth defects in animals and is therefore believed to cause fetal harm in humans. The benefits of its use to fight life-threatening cancers may outweigh the potential harm to a fetus.

Accutane (isotretinoin) should never be used in pregnancy. It is highly effective for treating severe cystic acne, but it causes serious birth defects. There are other drugs available to treat acne, and the disease is not life-threatening to the mother.

Who Should Paint the Nursery?

Chemicals--whether it's paint in the nursery or exhaust fumes in a parking garage--have long been suspected of causing birth defects. It's important for pregnant women to realize that most birth defects are not caused by a single factor, nor are they usually caused by faint traces of toxins. Scientists believe it takes a combination of factors to trigger a congenital malformation.

"Most birth defects have one or more genetic factors and one or more environmental factors," explains Richard Leavitt, director of science information at the March of Dimes.

Most of the chemicals a pregnant woman encounters pose little threat compared with the harm in smoking, drinking alcohol, or eating a poor diet.

"Most environmental exposure is at a low level compared to things you put in your mouth or inhale purposefully into your lungs," Leavitt says. "Public health warnings are aimed at the many to help the relatively few avoid a problem."

Daily, heavy exposure to chemicals may be dangerous, however. If a pregnant woman must work around fumes or chemicals, such as in a dry-cleaning business, art studio, or factory, she should use gloves, masks and adequate ventilation. But if she just gets a whiff of dry-cleaning fluid while picking up her laundry from the cleaners, there's little need to worry, Leavitt says.

Some environmental toxins such as lead are best avoided at any time, but especially during pregnancy. Scraping leaded paint off an old house window, drinking water from a pipe soldered with lead, or drinking out of decorative pottery containing lead can all potentially cause lead poisoning--and mental retardation--in a fetus. (See "Dangers of Lead Still Linger" in the January-February 1998 FDA Consumer.)

Radiation is also dangerous to developing babies. A pregnant woman who works in an x-ray department of a hospital must take precautions to avoid exposure. Elective dental x-rays should be postponed until delivery, and any nonpregnant woman who has an x-ray should have her reproductive organs shielded with a lead apron.

Taking hot baths, using saunas, or exercising in hot, humid weather can raise a woman's core temperature and have the potential to cause birth defects, especially in the first trimester. Lukewarm baths and moderate exercise are fine, however.

And what about computers or video display terminals? Although they have at times been accused of causing harm, there's probably no need to worry. Recent studies have not found any relationship between computer terminals and miscarriages.

And as for who should paint the nursery--today's paints don't contain lead and therefore probably aren't dangerous. But there are other reasons to find someone else to do this task. The repetitive motion of painting can be a strain on back muscles already under pressure from the extra weight of pregnancy, and standing on your feet for hours can make advanced pregnancy miserable. If someone else can do it, pass this chore along.

Of all the environmental harms, undoubtedly the most harmful is one women can control--smoking. Although there is no evidence smoking causes birth defects, it deprives the fetus of oxygen and leads to a number of problems. If all pregnant women avoided smoking, the United States would see a 5 percent reduction in miscarriages, a 20 percent reduction in low-birth-weight births, and an 8 percent reduction in premature deliveries in this country, according to the March of Dimes.

In the Family

Finally, a number of birth defects are inherited. They are usually triggered when the child inherits a matching pair of disease-causing genes, one from each parent. This is most often an issue for couples of similar ethnic or geographic origins.

For example, African-American couples are most at risk for having a child with sickle cell anemia. According to the March of Dimes, couples of Ashkenazic Jewish or French Canadian descent may be carriers of Tay-Sachs disease. People who know of genetic disorders in their families, or those who have already had one child with a disorder are also at a greater risk, as are couples who are closely related, such as first cousins. Genetic testing is available to determine the risk of passing some genetic disorders to an unborn child. Once a pregnancy begins, prenatal testing is available to detect a number of disorders, as well.

Some genetic abnormalities, such as Down syndrome (a genetic abnormality that causes mental retardation, short stature, and flattened features), increase with the parents' ages. Women over 35 are at higher risk of having a child with Down syndrome--about 1 in 100 for a 40-year-old, compared to 1 in 10,000 for a 20-year-old mother or 3 in 1,000 for a 35-year-old mother. And it's not always just the mother's age that matters. An estimated 25 percent of Down syndrome cases can be attributed to increased age of the father.

Finally, it's important to remember that for most healthy women, the incidence of birth defects is very low--less than 3 percent. And of malformations that do occur, the most common are also the most treatable. Cleft palate and club foot, two of the more common birth defects, can be surgically repaired. Many heart malformations can be repaired with surgery so that children live normal lives.

For the most part, health experts say, a woman can do a lot to ensure the health of her child by maintaining a healthy lifestyle.

Rebecca D. Williams is a writer in Oak Ridge, Tenn.

Accutane and Birth Defects

Accutane (isotretinoin), a relative of vitamin A, is approved to treat severe cystic acne that doesn't respond to other drugs. It has some serious side effects, though, especially if a woman taking it becomes pregnant.

The drug's manufacturer has included strong warnings in the package labeling to inform doctors and patients about the birth defects this drug can cause.

Pregnant women who take Accutane even for a short time are at great risk of having a baby with severe facial birth defects, malformed thymus glands, and mental retardation.

The risk is so great that any woman of childbearing age who is taking Accutane--even if she's not sexually active--must also use effective contraception at least one month before beginning Accutane, while using the drug, and for one month after stopping.


FDA Consumer magazine

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